Duty factor correction circuit

Claim 2

A circuit for providing duty factor correction with respect to an assymetrical input signal requiring same, said signal having relatively positive-going and relatively negative-going portions of unequal duration, said circuit comprising: limiting means receiving said assymetrical input signal for providing a substantially rectangular assymetrical current waveform by limiting the amplitude of said input signal, said rectangular current waveform having relatively positive-going and negative-going excursions, integrating means responsive to said current waveform positivegoing portions for producing an integral output increasing in a first sense, and responsive to said current waveform negativegoing portions for causing said integral output to decrease in the first sense, to produce a triangular waveform, and output means responsive to said triangular waveform for producing an output of a first relative polarity when the triangular waveform as received by the output means is above a predetermined reference value while producing an output of a second relatIve polarity when said triangular wave as received by the output means is below said predetermined reference value, said circuit including d.c. blocking alternating current coupling means for coupling said triangular wave-form as the input to said output means with the average value thereof coincident with said predetermined reference value.

Claim 3

The circuit according to claim 1 wherein said integrating means comprises capacitor means, said limiting means including means for providing a relatively constant current in a first direction relative to said capacitor means during said relatively positive-going portions of the input signal and for providing a relatively constant current in a second direction relative to said capacitor means during said relatively negative-going portions of the input signal.

Claim 4

The circuit according to claim 1 wherein said alternating current coupling means comprises a capacitor.

Claim 5

A circuit for providing duty factor correction with respect to an assymetrical input signal requiring same, said signal having two a.c. axis crossings per period, said circuit comprising: first limiting means receiving said assymetrical input signal for providing a substantially rectangular assymetrical current waveform by limiting the amplitude of said input signal, said rectangular current waveform having relatively positive-going and negative-going excursions of current above and below a predetermined reference value, integrating means for receiving said rectangular current waveform and providing a substantially triangular waveform in response to said rectangular current waveform, said integrating means having a time constant at least substantially as long as the period of said input signal, said triangular waveform having an average value dividing said triangular waveform into substantially equal time intervals, second limiting means responsive to the triangular waveform for providing a substantially rectangular output wave, as the input applied to such second limiting means varies above and below a predetermined reference value, and d.c. blocking alternating current coupling means for applying said triangular waveform to the second limiting means to provide said input varying with respect to said last mentioned predetermined reference value, said triangular waveform as thus applied to said second limiting means having substantially equal time intervals above and below the last mentioned reference value for producing a 50 percent duty factor output wave.

Claim 6

A circuit for providing duty factor correction with respect to an assymetrical input signal requiring same, said signal having two a.c. axis crossings per period, said circuit comprising: first limiting means receiving said assymetrical input signal for providing a substantially rectangular assymetrical current waveform by limiting the amplitude of said input signal, said rectangular current waveform having relatively positive-going and negative-going excursions of current above and below a predetermined reference value, integrating means for receiving said rectangular current waveform and providing a substantially triangular waveform in response to said rectangular current waveform, said integrating means having a time constant at least substantially as long as the period of said input signal, said triangular waveform having an average value dividing said triangular waveform into substantially equal time intervals, second limiting means responsive to the triangular waveform for providing a substantially rectangular output wave, as the input applied to such second limiting means varies above and below a predetermined reference value, and d.c. blocking alternating current coupling means for applying said triangular waveform to the second limiting means to provide said input varying with respect to said last mentioned predetermined reference value, said triangular waveform as thus applied to said second limiting means having substantially equal time intervals above and below the last mentioned reference value for producing a 50 percent duty factor output wave.

Claim 7

The circuit according to claim 4 wherein said integrating means includes a first capacitor.

Claim 8

The circuit according to claim 5 wherein said alternating current coupling means comprises a second capacitor.

Claim 9

The circuit according to claim 6 wherein said first limiting means includes an active switching device having its output terminal connected to said first capacitor, said circuit further including a resistor connected in charging relation to said first capacitor.

Claim 10

A circuit for providing duty factor correction with respect to an assymetrical input signal, said signal having two a.c. axis crossings per period, said circuit comprising, first limiting means receiving said assymetrical input signal for providing a substantially rectangular assymetrical current waveform by limiting the amplitude of said input signal, said rectangular current waveform having relatively positive-going and negative-going excursions of current above and below a predetermined reference value, integrating means for receiving said rectangular current waveform and providing a substantially triangular waveform in response to said rectangular current waveform, said integrating means having a time constant at least substantially as long as the period of said input signal, said integrating means including a first capacitor, said triangular waveform having an average value dividing said triangular waveform into substantially equal time intervals, second limiting means responsive to the triangular waveform for providing a substantially rectangular output wave, as the input applied to such second limiting means varies above and below a predetermined reference value, and alternating current coupling means for applying said triangular waveform to the second limiting means to provide said input varying with respect to said last mentioned predetermined reference value, said alternating coupling means comprising a second capacitor, said triangular waveform as thus applied to said second limiting means having substantially equal time intervals above and below the last mentioned reference value for producing a fifty percent duty factor output wave, said first limiting means comprising a pair of active current switching devices, one output of which is connected to the first capacitor, said pair of current switching devices being connected to switch current from one to the other when said input waveform reaches a predetermined value.

Claim 11

A circuit for providing duty factor correction with respect to an assymetrical input signal, said signal having two a.c. axis crossings per period, said circuit comprising, first limiting means receiving said assymetrical input signal for providing a substantially rectangular assymetrical current waveform by limiting the amplitude of said input signal, said rectangular current waveform having relatively positive-going and negative-going excursions of current above and below a predetermined reference value, integrating means for receiving said rectangular current waveform and providing a substantially triangular waveform in response to said rectangular current waveform, said integrating means having a time constant at least substantially as long as the period of said input signal, said integrating means including a first capacitor, said triangular waveform having an average value dividing said triangular waveform into substantially equal time intervals, second limiting means responsive to the triangular waveform for providing a substantially rectangular output wave, as the input applied to such second limiting means varies above and below a predetermined reference value, and alternating current coupling means for applying said triangular waveform to the second limiting means to provide said input varying with respect to said last mentioned predetermined reference value, said alternating coupling means comprising a second capacitor, said triangular waveform as thus applied to said second limiting means having substantially equal time intervals above and below the last mentioned reference value for producing a fifty percent duty factor output wave, said first limiting means comprising a pair of active current switching devices, one output of which is connected to the first capacitor, said pair of current switching devices being connected to switch current from one to the other when said input waveform reaches a predetermined value.

Claim 12

The circuit according to claim 8 wherein said current switching devices comprise differentially connected transistors having a common current source emitter resistor for returning the transistor emitters to a reference point.

Claim 13

A circuit for providing duty factor correction with respect to an assymetrical input signal, said signal having two a.c. axis crossings per period, said circuit comprising: first limiting means receiving said assymetrical input signal for providing a substantially rectangular assymetrical current waveform by limiting the amplitude of said input signal, said rectangular current waveform having relatively positive-going and negative-going excursions of current above and below a predetermined reference value, integrating means for receiving said rectangular current waveform and providing a substantially triangular waveform in response to said rectangular current waveform, said integrating means having a time constant at least substantially as long as the period of said input signal, said triangular waveform having an average value dividing said triangular waveform into substantially equal time intervals, second limiting means responsive to the triangular waveform for providing a substantially rectangular output wave, as the input applied to such second limiting means varies above and below a predetermined reference value, said second limiting means comprising a pair of current switching devices connected to switch current from one to the other when said triangular waveform as applied to said second limiting means reaches said last mentioned predetermined reference value, and alternating current coupling means for applying said triangular waveform to the second limiting means to provide said input varying with respect to said last mentioned predetermined reference value, said triangular waveform as thus applied to said second limiting means having substantially equal time intervals above and below the last mentioned reference value for producing a 50 percent duty factor output wave.

Claim 14

A circuit for providing duty factor correction with respect to an assymetrical input signal, said signal having two a.c. axis crossings per period, said circuit comprising: first limiting means receiving said assymetrical input signal for providing a substantially rectangular assymetrical current waveform by limiting the amplitude of said input signal, said rectangular current waveform having relatively positive-going and negative-going excursions of current above and below a predetermined reference value, integrating means for receiving said rectangular current waveform and providing a substantially triangular waveform in response to said rectangular current waveform, said integrating means having a time constant at least substantially as long as the period of said input signal, said triangular waveform having an average value dividing said triangular waveform into substantially equal time intervals, second limiting means responsive to the triangular waveform for providing a substantially rectangular output wave, as the input applied to such second limiting means varies above and below a predetermined reference value, said second limiting means comprising a pair of current switching devices connected to switch current from one to the other when said triangular waveform as applied to said second limiting means reaches said last mentioned predetermined reference value, and alternating current coupling means for applying said triangular waveform to the second limiting means to provide said input varying with respect to said last mentioned predetermined reference value, said triangular waveform as thus applied to said second limiting means having substantially equal time intervals above and below the last mentioned reference value for producing a 50 percent duty factor output wave.

Claim 15

The circuit according to claim 10 wherein said second limiting means comprises a differentially connected pair of transistors having a common emitter resistor returned to a reference point.

Claim 16

A circuit for providing duty factor correction with respect to an assymetrical input signal, said signal having two a.c. axis crossings per period, said circuit comprising: first limiting means receiving said assymetrical input signal for providing a substantially rectangular assymetrical current waveform by limiting the amplitude of said input signal, said first limiting means comprising a first differential pair of devices for switching current, said rectangular current waveform having relatively positive-going and negative-going excursions of current above and below a predetermined reference value, integrating means for receiving said rectangular current waveform and providing a substantially triangular waveform in response to said rectangular current waveform, said integratIng means having a time constant at least substantially as long as the period of said input signal, said integrating means comprising a pair of capacitors connected respectively to output electrodes of said devices of said first differential pair, said triangular waveform having an average value dividing said triangular waveform into substantially equal time intervals, second limiting means responsive to the triangular waveform for providing a substantially rectangular output wave, as the input applied to such second limiting means varies above and below a predetermined reference value, said second limiting means comprising a second differential pair of switching devices, and alternating current coupling means for applying said triangular waveform to the second limiting means to provide said input varying with respect to said last mentioned predetermined reference value, wherein said alternating current coupling means comprises RC coupling circuits connecting the said capacitors to respective inputs of the second pair of switching devices, said triangular waveform as thus applied to said second limiting means having substantially equal time intervals above and below the last mentioned reference value for producing a 50 percent duty factor output wave.

Claim 17

A circuit for providing duty factor correction with respect to an assymetrical input signal, said signal having two a.c. axis crossings per period, said circuit comprising: first limiting means receiving said assymetrical input signal for providing a substantially rectangular assymetrical current waveform by limiting the amplitude of said input signal, said first limiting means comprising a first differential pair of devices for switching current, said rectangular current waveform having relatively positive-going and negative-going excursions of current above and below a predetermined reference value, integrating means for receiving said rectangular current waveform and providing a substantially triangular waveform in response to said rectangular current waveform, said integratIng means having a time constant at least substantially as long as the period of said input signal, said integrating means comprising a pair of capacitors connected respectively to output electrodes of said devices of said first differential pair, said triangular waveform having an average value dividing said triangular waveform into substantially equal time intervals, second limiting means responsive to the triangular waveform for providing a substantially rectangular output wave, as the input applied to such second limiting means varies above and below a predetermined reference value, said second limiting means comprising a second differential pair of switching devices, and alternating current coupling means for applying said triangular waveform to the second limiting means to provide said input varying with respect to said last mentioned predetermined reference value, wherein said alternating current coupling means comprises RC coupling circuits connecting the said capacitors to respective inputs of the second pair of switching devices, said triangular waveform as thus applied to said second limiting means having substantially equal time intervals above and below the last mentioned reference value for producing a 50 percent duty factor output wave.

Claim 18

The circuit according to claim 12 wherein said integrating means further includes a pair of resistors connected respectively in charging relation to said capacitors.

Claim 19

The circuit according to claim 12 wherein said switching devices comprise transistors.

Claim 20

The circuit according to claim 14 wherein each pair of differentially connected transistors is provided with common emitter current source means.